JSON Web Token

JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. It is commonly used for Authentication and information exchange in web applications and APIs. JWTs are compact, self-contained tokens that can be verified and trusted because they are digitally signed.

A JWT consists of three parts: a header, a payload, and a signature. The header typically contains the type of token (JWT) and the signing Algorithm used (e.g., HMAC SHA256). The payload contains claims, which are statements about the user or other data. The signature is used to verify the authenticity of the token, ensuring that it hasn’t been tampered with.

The purpose of JWT is to provide a secure, efficient, and scalable way to transmit data and authenticate users. JWTs are commonly used for stateless Authentication in web applications, enabling the creation of single sign-on (SSO) systems, and allowing APIs to verify requests without needing to store session state on the server.

JWTs are generated by signing a header and payload with a secret key or public/private key pair. Once created, the JWT can be sent as an HTTP header or stored in cookies or local storage. When a server receives a JWT, it verifies the token’s signature using the appropriate key and extracts the payload to authenticate the user or validate their claims. JWTs are often used in conjunction with OAuth 2.0 and OpenID Connect for secure user Authentication.

Examples of using JWTs include issuing a token upon successful login, which the client can use to access protected resources in subsequent requests, and using JWTs to verify API requests by checking the token’s validity and claims. Many web frameworks and libraries support JWT for Authentication and Authorisation.

Potential issues with JWT include exposure to token theft if stored insecurely, improper handling of token expiration, and the risk of tampering if the signature verification is not correctly implemented. To mitigate these risks, developers should use secure storage mechanisms, enforce token expiration, and apply proper cryptographic practices for signing and verifying tokens.